1. Field of the Invention
The present invention relates to an oscillator circuit, and more particularly to an oscillator circuit having transistors forming a differential pair.
2. Description of the Related Art
Recently, with the Internet becoming rapidly widespread, demands for high-speed communication systems that can transmit and receive a large capacity of data are growing so that their bit rates tend to be more and more increasing. Nowadays, it is said that the bit rate has reached 160 G bps. Demands for wireless communication are also concurrently growing. To achieve these systems, an oscillator circuit used in both transmitter and receiver is important and indispensable.
Conventionally, LC oscillators have been used in which a loss generated in a resonator comprising an inductor (L) and a capacitor (C) is compensated by a negative resistance of a transistor to obtain continuous oscillation. Recently, so-called push-push oscillators utilizing harmonic waves have emerged, enabling the oscillator to oscillate with a higher frequency than the maximum oscillation frequency generated by a single transistor oscillator.
Low power oscillators or transmission systems, having a resonance circuit including a pair of transistors connected in cascade, are described in Japanese Patent Application Laid-Open No. 2000-307423. In Japanese Patent Application Laid-Open No. 2003-168924, a voltage control circuit utilizing a differential amplifier is described.